The present disclosure relates to an aromatic amine compound useful for an electron transport material, a hole transport material, or a luminescent material of an organic electroluminescent element, an organic electroluminescent element including the aromatic amine compound, and a display device including the organic electroluminescent element.
Recently, organic electroluminescent elements (EL elements) have attracted attention as one of flat panel displays that are self-luminous, that have a high response speed, and that do not have angle-dependent visibility, and thus interests in organic materials constituting such organic electroluminescent elements have been increasing. In particular, among such organic materials, there are few materials that can form a stable blue-light-emitting layer, which is an important problem to be solved in order to realize a full-color organic electroluminescent element.
In order to realize a high luminance and a high efficiency of an organic electroluminescent element, a doping method has been employed in which a light-emitting layer is constituted by a host compound and a guest compound (dopant). By selecting a host compound having a high energy transfer efficiency from the host compound to the dopant compound, the luminous efficiency of the organic electroluminescent element can be increased. For example, it is known that 9,10-diphenylanthracene compounds can be used as an electron-transporting host or a hole-transporting host.
Aromatic amines have been actively studied as a photosensitive material for electrophotography. Subsequently, it has been reported that aromatic amines exhibit excellent characteristics as a hole transport material of an organic electroluminescent element. Consequently, a large number of such compounds have been reported. Recently, the use of an aromatic amine as a light-emitting layer has also been proposed.
An organic layer constituting an organic electroluminescent element is formed by using various organic materials as described below.
Japanese Patent No. 3506281 (paragraphs 0006 to 0010, 0079, and 0085) titled “organic electroluminescence element” discloses an organic electroluminescent element including an organic compound layer having at least a recombination region where a hole and an electron are recombined and a light-emitting region that emits light in response to the recombination, and a pair of electrodes sandwiching the organic compound layer, in which the recombination region and/or the light-emitting region contains an aromatic amine as a fluorescent dopant and a distyryl arylene compound as a luminescent material (host material). According to the organic electroluminescent element described in Japanese Patent No. 3506281, at least one of the recombination region where a hole and an electron are recombined and the light-emitting region that emits light in response to the recombination contains a fluorescent dopant having a specific structure. For example, the luminescent color is not significantly changed even after this organic electroluminescent element is driven for a long time, and thus the organic electroluminescent element has a long life time. In addition, the organic electroluminescent element has a high luminous efficiency. Accordingly, the organic electroluminescent element is suitably used as, for example, a display of a device used in the information industry.
Japanese Patent No. 3104223 (paragraphs 0006 to 0008 and 0123) titled “organic electroluminescent element” describes that when a perylene compound is used as a mixture with an aromatic amine compound, aromatic diamine compound, or aromatic triamine compound having a specific aromatic hydrocarbon or aromatic heterocyclic ring as a substituent, a red-light-emitting organic EL element having particularly good characteristics can be obtained.
Japanese Patent No. 3011165 (paragraphs 0008 to 0010 and 0196) titled “organic electroluminescent element” describes that when a 5-cyanopyrromethene-BF2 complex is used as a mixture with an aromatic amine compound, aromatic diamine compound, or aromatic triamine compound having a specific aromatic hydrocarbon or aromatic heterocyclic ring as a substituent, a red-light-emitting organic EL element having particularly good characteristics can be obtained.
Japanese Patent No. 3092584 (paragraphs 0008 to 0010 and 0142) titled “organic electroluminescence element” describes that bis-2,5-(2-benzazoyl)hydroquinone compound is used as a mixture with an aromatic amine compound, aromatic diamine compound, or aromatic triamine compound having a specific aromatic hydrocarbon or aromatic heterocyclic ring as a substituent, a red-light-emitting organic EL element having particularly good characteristics can be obtained.
Japanese Unexamined Patent Application Publication No. 2001-257074 (paragraphs 0004 to 0006 and 0017) titled “hydrocarbon compound and organic electroluminescent element” discloses an organic electroluminescent element including a pair of electrodes and at least one layer containing at least one 9,10-di(3′-fluoranthenyl)anthracene derivative and disposed between the electrodes.
Japanese Unexamined Patent Application Publication No. 2002-69044 (paragraphs 0004 and 0011) titled “organic electroluminescence element” describes that by adding a novel hydrocarbon compound in which an aryl structure is bonded to a fluoranthene structure to an organic compound film, heat resistance of an organic electroluminescence element is improved, and furthermore, a hole-transporting property and an electron-transporting property are improved to realize a high luminous efficiency.
Japanese Unexamined Patent Application Publication No. 2000-182776 (paragraphs 0008 to 0013) titled “organic multilayer electroluminescence element” discloses an anthracene derivative as a typical example of a material of a hole-transporting layer.
Japanese Patent No. 3838816 (paragraphs 0009 to 0012) titled “compound for organic EL element” discloses a phenylanthracene derivative used as a compound for an organic EL element.
Japanese Unexamined Patent Application Publication No. 2001-335516 (paragraphs 0004 to 0014) titled “organic electroluminescence element” discloses a compound having a diphenylanthracene structure in the center thereof and a specific structure substituted with aryl groups in the terminals thereof.
Japanese Unexamined Patent Application Publication No. 2002-260861 (paragraphs 0004, 0005, and 0013) titled “organic light-emitting device” discloses benzenoid compounds which include a polycyclic aromatic hydrocarbon (PAH) and a combination of two or more PAHs (including benzene, naphthalene, and anthracene) and which are suitable for a host component of a light-emitting layer of an organic light-emitting device.
Furthermore, Japanese Patent No. 4041816 (paragraphs 0004 to 0006, and 0021) titled “organic electroluminescence element and anthracene derivative” discloses an anthracene derivative for realizing an organic EL element.
In Japanese Patent No. 3092584, red-light emission is realized by forming a light-emitting layer composed of a mixed layer of bis-2,5-(2-benzazoyl)hydroquinone compound and an aromatic amine compound. In Japanese Patent No. 3011165, red-light emission is realized by forming a light-emitting layer composed of a mixed layer of 5-cyanopyrromethene-BF2 complex and an aromatic amine compound. In Japanese Patent No. 3104223, red-light emission is realized by forming a light-emitting layer composed of a mixed layer of a perylene compound and an aromatic amine compound. However, the emission luminance obtained by these techniques is low, and thus the red-light emission is not sufficient for practical use.
In the development of an organic electroluminescent element, selection of a light-emitting material is the most important factor for ensuring the reliability of the element. Among materials that can be used as a red-light-emitting material, there are few materials which have good color purity and a high fluorescence quantum efficiency, and which can be formed into a stable amorphous thin film. Furthermore, the realization of a red-light-emitting element that has a high luminance, that is stable, and that has high color purity has been desired.
It is desirable to provide an aromatic amine compound that can be suitably used for forming an organic layer constituting an organic electroluminescent element and that can emit red light with a high fluorescence quantum efficiency, an organic electroluminescent element including the aromatic amine compound, and a display device including the organic electroluminescent element.